DE102016005949A1 - Method for cleaning and checking the technical cleanliness of a drive train surface - Google Patents

Abstract

The invention relates to a method for cleaning and checking a surface (12) of a component (10), in which the surface (12) is cleaned by means of at least one laser beam and checked by laser-induced plasma spectroscopy, wherein a plurality of mutually different locations (Mn) of the surface (12) are checked by means of laser-induced plasma spectroscopy by determining respective measured values characterizing the respective points (Mn) by means of laser-induced plasma spectroscopy, the surface (12) being checked as a function of the measured values.

Description

The invention relates to a method for cleaning and checking a surface, in particular for a vehicle, according to the preamble of claim 1.

Such a method for cleaning and checking a surface of a component is already well known from the general state of the art. In the method, the surface is cleaned by means of at least one laser beam and checked by means of laser-induced plasma spectroscopy. In particular, the surface can be checked for its cleanness by means of laser-induced plasma spectroscopy, in the framework of which at least one laser is used, by means of which at least one laser beam is emitted for carrying out the laser-induced plasma spectroscopy. Usually, the laser is pulsed, so that the laser emits laser beam pulses or laser pulses, by means of which the laser-induced plasma spectroscopy is performed.

Since the surface is cleaned by means of at least one laser beam, a so-called laser cleaning is performed to clean the surface. Here too, for example, laser beam pulses or laser pulses are used to clean the surface. It is known to use the laser-induced plasma spectroscopy as a process control in laser cleaning, for example, to check the laser cleaning, in particular their effectiveness in terms of cleaning the surface by means of laser-induced plasma spectroscopy. Typically, laser-indicated plasma spectroscopy is also referred to as LIPS or LIBS (Laser Induced Breakdown Spectroscopy).

Object of the present invention is to develop a method of the type mentioned in such a way that the surface can be checked very precisely.

This object is achieved by a method having the features of claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

In order to further develop a method specified in the preamble of claim 1 such that the surface can be checked particularly precisely, it is provided according to the invention that a plurality of mutually different locations of the surface are checked by means of laser-induced plasma spectroscopy, by means of laser-induced plasma spectroscopy, the respective positions characterizing measured values are determined, wherein the surface is checked in dependence on the measured values. The named areas of the surface are measuring points at which the surface is checked by means of laser-induced plasma spectroscopy. In the context of laser-induced plasma spectroscopy, for example, the respective points are acted on by means of at least one laser beam, in particular by means of at least one laser pulse, in order thereby to carry out the laser-induced plasma spectroscopy. The laser pulse performed in the context of laser-induced plasma spectroscopy is a measuring pulse, which is also referred to as measuring laser pulse or laser measuring pulse. By means of the measuring pulse, material is removed from the surface at the respective measuring point within the scope of laser-induced plasma spectroscopy. This removed material, which originates for example from at least one layer of the surface, is converted, in particular by means of the measuring pulse, into a plasma whose emission can be recorded or measured and spectrally evaluated by means of a spectrometer.

By means of this evaluation, for example, the correlation coefficient r, in particular the linear correlation coefficient r, is determined, wherein the correlation coefficient r is the aforementioned measured value. The surface is checked and evaluated by comparing the recorded spectrum, for example, with a reference spectrum of a sufficiently clean reference surface via the linear correlation according to Bravais and Pearson. The correlation coefficient r is therefore a measure of the relative technical cleanliness of the surface, which is designed, for example, as a functional surface, in particular as a joining surface. In this case, the aforementioned reference surface is preferably formed from the same base material as the surface to be checked. Thus, for example, the technical cleanliness of the surface is checked by means of the method. The surface is, for example, a surface of a drive train, in particular for a motor vehicle, which is drivable by means of the drive train. This means that the surface is formed for example by a component of the drive train, which is also referred to as powertrain.

The idea underlying the invention is not only to check and evaluate the surface at one point or at one point, but according to the invention, respective measured values, in particular in the form of correlation coefficients r, are determined at several points of the surface measured values is checked. As described above, it is thus possible, the technical cleanliness of the surface very precise and meaningful to convey. By checking the respective locations of the surface, a cleaning or cleanliness map of the surface can be created, wherein the measured values or the locations represent respective points of this cleanliness map. On the basis of the multiple measured values, it is thus possible to realize a full-surface examination of the surface, although not necessarily a full-surface measurement is necessary. As part of the determination of the measured values, it is possible that the measuring points overlap each other, for example, to scan the surface over its entire surface and thus to check. In contrast, however, it is also conceivable that the measuring points are arranged without overlapping each other, so that the measuring points do not overlap each other, the measuring points can be spaced apart. As a result, the surface is not scanned over the entire surface, but due to the fact that a plurality of measuring points is checked, a particularly precise and meaningful inspection of the surface as a whole is possible.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

The drawing shows in:

1 a schematic plan view of a component whose surface is cleaned and checked by a method according to a first embodiment, wherein the surface is cleaned by means of at least one laser beam and checked by means of laser-induced plasma spectroscopy;

2 a further schematic plan view of the component for illustrating the method;

3 a schematic plan view of a component whose surface is cleaned and checked by the method according to a second embodiment;

4 a diagram illustrating the method; and

5 another diagram illustrating the method.

In the figures, identical or functionally identical elements are provided with the same reference numerals.

1 and 2 show a component 10 which is presently designed as a ring and a surface 12 which is cleaned and checked by a method according to a first embodiment. As part of the procedure, the surface becomes 12 cleaned by means of at least one laser beam and checked by means of laser-induced plasma spectroscopy (LIPS or LIBS). For this purpose, at least one laser is used, which provides at least one laser beam. By means of this laser beam is the surface 12 cleaned and / or checked. Because the surface 12 is cleaned by means of the laser beam, the surface becomes 12 cleaned by means of a so-called laser cleaning. Furthermore, laser-induced plasma spectroscopy is carried out by means of the laser beam. For cleaning and for checking, that is to carry out laser-induced plasma spectroscopy, the laser is pulsed, so that the laser provides the laser beam as a laser pulse, which is also referred to as a laser beam pulse.

In the context of laser-induced plasma spectroscopy, the laser pulse is also referred to as measuring pulse, since - as will be explained in more detail below - the surface 12 is checked by means of a plurality of such laser pulses or measuring pulses. In the context of laser cleaning, the laser pulse is also referred to as a cleaning pulse, since the surface 12 For example, by means of a plurality of such laser pulses or cleaning pulses is cleaned. As part of the laser cleaning, for example, by means of the respective cleaning pulse material of the surface 12 or from the surface 12 removed, this material is also referred to as ablated material. Also in the context of laser-induced plasma spectroscopy, material of the surface is generated by means of the respective measuring pulse 12 removed, wherein the removed material is transferred into a plasma, whose emission is recorded and evaluated spectrally by means of a spectrometer. In the context of this spectral evaluation, a spectrum is recorded as the actual spectrum, which is compared, for example, with a reference spectrum as the desired spectrum. Checking the surface 12 This is done, in particular, by comparing the recorded actual spectrum with the reference spectrum of a sufficiently clean reference surface via the linear correlation according to Bravais and Pearson, by determining the linear correlation coefficient r. This linear correlation coefficient r is therefore a measure of the relative technical cleanliness of the surface 12 which is designed, for example, as a functional surface, in particular as a joining surface. Under the Joining surface is for example to understand that the component 10 Connected via the joint surface with another component, that is joined.

In the first embodiment, at least one cleaning process is first carried out, in the scope of which the laser cleaning is carried out, so that by means of the cleaning process, the surface 12 is cleaned by means of a plurality of cleaning pulses. After this conventional laser cleaning, which is also referred to as laser beam cleaning, the laser-induced plasma spectroscopy is performed. In this case, a plurality of mutually different points M _{n are} checked by means of laser-induced plasma spectroscopy by determining respective measured values characterizing the respective points M _n by means of the laser-induced plasma spectroscopy, wherein the surface 12 is checked depending on the measured values. The respective measured value is the aforementioned correlation coefficient r, which is determined for each point M _n . Where n is the number of digits, where n is an integer positive number greater than zero. The points M _n are thus measuring points at which the laser-induced plasma spectroscopy is performed so that the surface 12 At least one measuring pulse is applied to the measuring points in order to determine the linear correlation value r at the respective measuring point.

The number n of measuring points should be a sample size determined according to the desired significance. About the respective correlation coefficient r is a statement about the relative technical cleanliness of the surface 12 , The aim is a statistical evaluation and assurance of the relative technical cleanliness of the surface 12 , Out 1 It can be seen that the measuring points, for example, in the circumferential direction of the component 10 are arranged consecutively and are, for example, spaced from each other, so that on the basis of the measuring points and on the basis of the associated measured values a cleaning map of the surface 12 can be determined.

According to 2 In addition, the respective locations M _{n are} additionally provided with the index i, where i indicates the number of cleaning operations. In this case, i is an integer natural number and greater than 0. After carrying out a first laser beam cleaning (i = 1), the points M _n.1 are checked in the manner described, whereby here too the number n should be a sample size determined according to the desired significance , The respectively associated correlation coefficient r for each position M _n.1 allows a statement about the relative technical cleanliness.

The correlation coefficient r is compared, for example, as an actual value with a desired value r _soll . If the actual value is greater than the target value, the surface points 12 at the respective measuring point a sufficient cleanliness. If the actual value does not exceed the setpoint value at all measuring points, a second laser beam cleaning, that is to say a second cleaning process (i = 2), is carried out. This means that the second cleaning process is connected in time to the checking of the points M _n.1 , wherein the checking of the points M _n.1 follows the cleaning process in time. If, for example, at least one of the determined correlation coefficients is below the associated desired value, the second cleaning process is carried out after the correlation coefficients r have been determined for the respective measuring points.

After the second cleaning process, further points M _{n.2 of} the surface 12 checked by means of laser-induced plasma spectroscopy, wherein the locations M _{n.2 are} at least partially different from the first locations M _n.1 . This alternate performing a cleaning process and a subsequent verification of the surface 12 at respective measuring points is an iteration or an iterative method that is carried out or until the correlation coefficient r exceeds the setpoint value r _soll as the actual value at all measuring points.

Out 1 and 2 It can be seen that in the first embodiment, the cleaning test is performed on a circular ring with the area A _K , wherein in the first embodiment, a separate laser cleaning and measurement are provided, as the respective cleaning process and the respective, subsequent verification of the measuring points of the surface 12 be performed consecutively in time or successively and thereby separated from each other. This means that the performance of the laser-induced plasma spectroscopy during the cleaning process is omitted.

3 illustrates a second embodiment of the method, wherein the cleaning and measurement or inspection of the surface 12 done by the same laser pulse. This means that in the first embodiment the respective cleaning pulse is used as the respective measuring pulse, so that the abovementioned plasma of each cleaning pulse is checked or analyzed at the respective point M _n by means of the laser-induced plasma spectroscopy. Also with reference to the second embodiment, n denotes the number of measuring points at which the surface 12 is cleaned and also checked, since the cleaning pulse is used as a measuring pulse. Thus, in the second embodiment, a statement about the relative technical cleanliness is made about the correlation coefficient r at each point M _n at each Cleaning pulse, where n is a whole positive number and greater than 0.

In the second embodiment, it is provided that, for example, first the first point M _{1 is} cleaned and checked by means of the laser pulse. The second location M ₂ is cleaned and checked only after cleaning and after checking the first location M ₁ . In this case, the second point M _{2 is} first charged with a laser pulse for cleaning and checking the second position M ₂ when the correlation coefficient belonging to the first position M ₁ exceeds the setpoint value as the actual value. In other words, the second location M _{2 is} not cleaned and checked until the correlation coefficient belonging to the first location M ₁ exceeds the corresponding desired value.

In order to apply the points M _n successively, that is successively or successively with at least one laser pulse, which is used both as a cleaning pulse and as a measuring pulse, the laser or the laser beam or laser pulse becomes relative to the component 10 emotional. It can be provided that the laser remains stationary while the component 10 is moved relative to the laser. Alternatively, it is conceivable that the component 10 remains stationary while the laser is relative to the laser 10 is moved. If, for example, the correlation coefficient r belonging to the first position M _{1 is} initially below the desired value, the first point M _{1 is} cleaned and checked again before the measuring point M ₂ is cleaned and checked. The first digit M ₁ is cleaned and checked until the correlation coefficient r belonging to the first position M ₁ exceeds the nominal value. Only then is the second location M ₂ cleaned. This procedure, which has been described with regard to the first location M ₁ and the second location M ₂ , can be transferred analogously to the other locations M _n . Thus, several cleaning pulses are possible per location M _n , which are used simultaneously as measuring pulses for performing the laser-induced plasma spectroscopy.

For example, a conventional implementation of laser beam cleaning with a line frequency f _L and a pulse repetition frequency f _{P can be provided} at a pulse duration t _{P of} the respective laser pulse. By way of example, the measurements or checks of the plasma of the cleaning pulses take place by means of one or more high-speed spectrometers, which have, for example, a recording frequency f _A of substantially more than 10 Hz. Depending on the process parameters, the plasma of each cleaning pulse or of every second, third, fourth, tenth cleaning pulse can be detected. The evaluation of the relative technical cleanliness takes place via the correlation coefficient r for the measured cleaning pulses in real time and, for example, as a representation in a graph in which the correlation coefficient r is represented as a function of the number n of the cleaning pulse or a rotation angle φ of a rotation axis. To this axis of rotation, for example, the component 10 rotated by a respective rotation angle φ, thereby to apply the respective points M _n to the respective laser pulse. The cleaning is terminated, for example, if the respective correlation coefficient r for Δφ = 360 ° exceeds the respective setpoint value, in particular in the case of rotationally symmetrical surfaces, or if the setpoint value for an entire length of the surface 12 coherently reached or exceeded.

4 shows a diagram whose ordinate 14 the correlation coefficient r is plotted. On the abscissa 16 of the diagram, the number n of the respective laser pulse or the rotation angle φ is plotted around the axis of rotation in the unit degrees. Furthermore, a line illustrates 18 the target value r _soll . In the in 4 Diagram shown is a gradient 20 registered, which illustrates the correlation coefficient r as a function of the number n or of the rotation angle φ. It is off 4 recognizable that the correlation coefficient r in a range b for Δφ = 360 ° is contiguous above the desired value r _soll , so that the cleaning is terminated.

5 shows a diagram illustrating a LIBS based cleanliness mapping. In 5 For example, the surface to be checked is designated by A, the surface A being subdivided into a plurality of surface elements. In this case, LIBS measurements of the plasma of a respective measuring pulse are carried out for the respective surface element MA. In this way, the entire surface A is scanned with m rows and n columns. For each surface element MA with the coordinates m and n, the associated correlation coefficient r _{mn is} determined. Finally, for example, a false color representation of the surface A is created based on the respective correlation coefficient r _mn for each surface element MA. This means that in 5 surface elements MA shown in color as a function of the respective correlation coefficient r _mn, for example, to illustrate whether the respective, belonging to the respective surface element MA correlation coefficient r _mn as an actual basis of this color representation or on the basis of the respective color of the respective surface element MA Value exceeds the respective nominal value or not. In particular, this colored representation can be used to illustrate the extent to which the actual value exceeds the setpoint value, that is to say that the color representation can be used to illustrate a difference between the setpoint value and the actual value. As a result, a false-color representation of the relative technical cleanliness of the surface A designed, for example, as a functional surface can be realized by the cleanliness mapping.

Claims (7)

Method for cleaning and checking a surface ( 12 ) of a component ( 10 ), in which the surface ( 12 ) is cleaned by means of at least one laser beam and checked by means of laser-induced plasma spectroscopy, characterized in that a plurality of mutually different locations (M _n ) of the surface ( 12 ) can be checked by means of laser-induced plasma spectroscopy by determining respective measured values characterizing the respective positions (M _n ) by means of laser-induced plasma spectroscopy, the surface ( 12 ) is checked depending on the measured values. A method according to claim 1, characterized in that initially at least one cleaning operation is performed, by means of which the surface is cleaned by means of the laser beam, after which the measured values are determined. A method according to claim 2, characterized in that the respective measured value is compared with a desired value. A method according to claim 3, characterized in that after the determination of the measured values, at least one further cleaning process is performed when at least one of the measured values is below the associated desired value. Method according to one of the preceding claims, characterized in that after cleaning a first of the points (M _n ) and before cleaning a second of the points (M _n ) the first point (M ₁ ) is checked by means of laser-induced plasma spectroscopy. A method according to claim 5, characterized in that the second point (M ₂ ) after the first point (M ₁ ) is cleaned when the measured value of the first point (M ₁ ) exceeds a desired value. Method according to claim 5 or 6, characterized in that the respective location (M _n ) of the surface ( 12 ) is cleaned by means of at least one laser pulse, which is used as a laser pulse for performing the laser-induced plasma spectroscopy.

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